Luminescent europium(III) complexes of tripodal heptadentate N₇ ligands containing three imidazole groups

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• 作者：Saori Takahashi^a ; Shingo Hashimoto^a ; Yohei Shimogori^a ; Naohide Matsumoto^a ; ^{naohide@aster.sci.kumamoto-u.ac.jp"" rel=""nofollow} ; Toshio Nakashima^b ; Masanobu Tsuchimoto^c
• 关键词：Europium(III) complex ; Tripodal ligand ; Imidazole group ; Crystal structure ; Photoluminescence
• 刊名：Polyhedron
• 出版年：2011
• 出版时间：2 August 2011
• 年：2011
• 卷：30
• 期：12
• 页码：2026-2031
• 全文大小：1006 K

文摘

Luminescent Eu^III complexes with tripodal heptadentate N₇ ligands containing three imidazole groups, [Eu^III(H₃L^2-H)(ac)](ClO₄)₂·H₂O (1), [Eu^III(H₃L^2-Me)(ac)](ClO₄)₂·2EtOH (2), and [Eu^III(H₃L^4-Me)(ac)](ClO₄)₂·H₂O (3), were synthesized and characterized, where H₃L^2-H, H₃L^2-Me, and H₃L^4-Me are the tripodal ligands derived from the 1:3 condensation of tris(2-aminoethyl)amine and either 4-formylimidazole, 2-methyl-4-formylimidazole, and 4-methyl-5-formylimidazole, respectively, and ac denotes an acetate ion. Single-crystal X-ray analyses revealed that each Eu^III ion is coordinated by a tripodal heptadentate N₇ ligand and two oxygen atoms of the acetate ion as a bidentate ligand. The complexes displayed sharp emission bands based on the f–f transitions by excitation at 261 nm in acetonitrile. The emission intensities increased in the order 1 < 2 < 3 in acetonitrile, while the emission spectra were quenched in aqueous solution due to the partial dissociation of the acetate ion and tripodal ligand.